Fix Document class

[jbrown-xentity]

Name: James Brown

Affiliation: GSA/data.gov

Type of issue: Schema - Document class

Issue: There are a number of issues with this class, namely that it doesn't have a link to the document! This was discovered because mediaType field is an array, which also seems wrong (the type should correspond to a single document which is what this seems to be describing)

• https://github.com/GSA/dcat-us/blob/main/jsonschema/definitions/Document.json, and documentation

Recommended change(s):
A clearly defined way to link to the document must be created, defined in documentation, and make this required (otherwise what is the point of providing Document metadata?)
Also, should fix the mediaType field to be a single value, and not an array of values.

[jbrown-xentity]

Summary from conversation of Tiger Team:

• Keep the class, it is distinct from distribution
• Add accessURL and downloadURL, but make both optional
• Consider other detail cleanup from refactor Document.json #77